| 摘要 |
PURPOSE:To output the sum of input voltages as a current with a simple circuit and to improve the characteristic in reducing the power supply voltage by using a current mirror as a feedback circuit of an operational amplifier and connecting a resistor between an input terminal and an inverting input of the operational amplifier. CONSTITUTION:Denoting the area ratio of transistors (TR) 3,2 as 1:m when the hFE of TRs constituting a current mirror circuit 15 is sufficiently high, the output current I0 is expressed as I0=m.Iia=(m/R).Via, which indicates that an output current proportional to the input voltage Via is obtained. When n-set of input terminals 8a-8n are provided, the resistance value of corresponding resistors 4a-4n is R and input voltages Via-Vin are impressed respectively, then the total sum of the input currents is Ii=(Via+... +Vin)/R. The sum current flows to the current mirror circuit 15, the output current I0=m.(Via+... +Vin)/R is obtained, which is an output current proportional to the sum of the input voltages.
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